Early computer designs generally included a chassis with a plurality of individual components and assemblies mounted therein and connected to one another by means of wires, cables, brackets, nuts, bolts and the like. A major computer design advance occurred with the advent of printed circuit boards, integrated circuits and modular component assemblies. The printed circuit boards were, for example, formed of lightweight material and housed a myriad of components which were electrically interconnected with the component assemblies through wiring harnesses. The wiring harnesses and hard wire connections were subsequently replaced by technologically advanced connectors used for integrally coupling the individual components to each other and to other circuitry in the computer.
In the design of electronic equipment, the use of connectors, modular components, and specialized hardware has permitted key components and printed circuit boards to be efficiently added and removed. Such ease in the addition and deletion of computer components and printed circuit boards has facilitated assembly repair, upgrade, and/or changes in functionality.
Computer reliability and serviceability are also valuable design aspects. Originally, a rule of practice in the maintenance of electrical circuitry, such as computer hardware, was that of always turning the power to the computer off before components or printed circuit boards were added or removed from the computer chassis or support frame. Recent innovations have addressed the desirability to insert and remove modular components and printed cards from electrical equipment, such as computer hardware, when the computer is electrically connected and operational, i.e. “hot.” This is now possible for hot-pluggable hard drives, and in these cases, the power may be disconnected from only the connector of the drive to be inserted and removed while allowing the adjacent components to remain “hot.”
Removable computer components today include disc drives, drive cages, fans, power supplies, system I/O modules, processor boards, and other subassemblies. As referenced above, the removability of computer components allows for better overall serviceability of the computer system, which is a distinct advantage to both the user and the maintenance technician. A defective power supply in the main or central computer generally requires prompt replacement in order to limit downtime. It is for this reason that modular components and connectors facilitate prompt replacement and are thus popular in many computer designs.
The modularity of computer systems is thus recognized as an important design consideration. As referenced above, modules can be removed and examined for operability or other purposes much easier than permanently mounted fixtures within a computer chassis. Because computers provide an integral part of most business operations, it is of utmost importance to maintain the reliability and integrity of the computer system. When the various elements of a computer can be easily removed in a modular form, they can also be replaced to maintain the operational status of the computer.
Despite the advantages of allowing electrical components of a computer system to be hot-pluggable there are certain concerns and potential problems associated with hot-pluggable computer systems. In order to prevent damage to the hot-pluggable component and the computer system and to prevent electrical shock to a user inserting or removing the hot-pluggable component, computer systems include a mechanical switch associated with each hot-pluggable component connector which must be physically switched off and on during removal and insertion of the hot-pluggable component. The mechanical switch adds cost to the computer system, requires additional space for locating the switch, and can reduce reliability of the overall computer system due to the mechanical nature of the switches.
It would be advantageous, therefore, to devise a method and apparatus for detecting the presence of hot-pluggable components in a computer system without the use of mechanical switches.